Did you by any chance completely reinstall LFS? As you might now the LFS AI "learns" the tracks. Their knowledge is stored in a folder in Live for Speeds data directory, if you did a fresh install you will have to move that data to your new installation.
Maybe you're just running new combos which your AIs haven't learned yet?
Or has the "AI user player setup" setting changed?
Maybe you've become a better driver?
I am quite sure no work has been done when it comes to the AI. Not yet!